Method of fixing photographic material containing a free radial producing compound

ABSTRACT

Light-sensitive photographic material comprising a lightsensitive generator of free radicals and a color modifier capable of showing a visible color change by the action of such free radical is fixed against photolytic color change by contact with a salt of hydrogen sulfide or a salt of a sulfur-containing oxygen acid.

United States Patent METHOD OF FIXING PHOTOGRAPHIC MATERIAL CONTAINING AFREE RADICAL PRODUCING COMPOUND 6 Claims, No Drawings U.S. Cl 96/48,96/90 Int. Cl G03c 5/24 Field of Search 96/48, 90

[56] References Cited UNITED STATES PATENTS 3,255,013 6/l966 Dersch etal 96/67 X 3,374,094 3/1968 Waener et al.... 96/67 X 3,512,976 5/1970Yamada et al 96/48 OTHER REFERENCES Kasor, Light-Sensitive Systems, JohnWiley & Sons, TR 350 A5 C2 pg. 365 8/27/65 irimary Examiner-Norman G.Torchin Assistant Examiner-Richard E. F ichter Attorneys-J. RussellJuten, Peter F. Willig, Lionel N. White and Milford A. Juten ABSTRACT:Light-sensitive photographic material comprising a light-sensitivegenerator of free radicals and a color modifier capable of showing avisible color change by the acnon of such free radical lS fixed againstphotolytic color change by contact with a salt of hydrogen sulfide or asalt of a sulfur-containing oxygen acid.

METHOD OF FIXING PHOTOGRAPIIIC MATERIAL CONTAINING A FREE RADICALPRODUCING COMPOUND BACKGROUND in the material, to provide a reproductionof the image. Subsequent to the desired imagewise exposure, however, ithas been found necessary to fix the material against further lightexposure in order to prevent undesirable background fogging and loss ofimage.

In the prior art, fixation of a light-sensitive photographic material ofthe above-specified type was accomplished by a thermal fixing method ora solvent fixing method. In the former fixing method the light-sensitivephotographic material on which an image is formed by irnagewise exposureto light is heated so that the remaining light-sensitive componentdecomposed or sublimed. The photographic material then no longer showscolor change when exposed to light.

Among the light-sensitive photographic materials which are effective forthennal fixation, there are, for example, a composition which comprisesdiphenyl amine and carbon tetrabromide, and one which comprisesbrilliant green and carbon tetrabromide. Besides the above-indicatedcarbon tetrabromide, aroyl trihalogenated hydrocarbons are preferred asphotoactivators. As is well known, however, carbon tetrabromide isextremely toxic and volatile at an elevated temperature. Duringhandling, therefore, a special care should be taken to prevent frominhalation of the carbon tetrabromide vapor. Aroyl trihalogenatedhydrocarbon also is incon- .venient because of its lachrymatory natureand volatility. Furthermore, a light-sensitive photographic compositionwhich is used in a thermally fixable, light-sensitive photographicmaterial should be readily heat-decomposable or sublimable, and suchlight-sensitive photographic composition usually is rather unstable evenat an ordinary temperature.

' Thus, a light-sensitive photographic material useful in thermalfixation has rather poor storage ability, whereas a well storablelight-sensitive photographic material is not so suitable for thermalfixation.

Another fixing method is a solvent fixing process wherein alight-sensitive photographic material is treated with an appropriatesolvent to remove the residual light-sensitive component so that the thephotographic material becomes insensitive to further light-exposure. Itis essential to use a solvent that dissolves the residuallight-sensitive component well, but does not dissolve the formed image.If a solvent is used which has even a little dissolving power for theimage, an unsatisfactory reproduction will be obtained due to loweredresolution resulting from the exudation of the image. Suitable solventsfor solvent fixing process are very few and they are expensive, andtherefore, it is a difiicult problem to find an appropriate solvent.Furthermore, the solvent-fixing process is to wash out so-callednonimage area, and so, it is required for complete washing-out to use aselected solvent in large amount or to replenish a fresh solvent fromtime to time. Thus, this process is rather expensive and impractical.

SUMMARY OF THE INVENTION An object of the present invention is toprovide a fixing method which effectively prevents postexposure foggingof the noted type of photographic material, which has no adverseinfluence on the quality of an image formed, and which is free fromhealth hazard.

This object can be achieved and the drawbacks encountered in the priorart can be overcome by using a water-soluble salt of hydrogen sulfide ora water-soluble, reducing salt of a sulfur-containing oxygen acid as afixing agent in accordance with a method of the present invention. Thefixing agents are used in the form of aqueous solutions which may beapplied to exposed light-sensitive photographic materials. Exposedlightsensitive photographic materials are coated with or dipped intoaqueous solutions containing the fixing agents. The fixing agents usedin this invention diminish the photo activity of a photoactivatorremaining intact, i.e. which do not take part in image formation, by achemical reaction in which such agents capture halogen contained in thephotoactivator to render the activator inactive.

Typical compounds useful as fixing agents referred to above are asfollows:

Sodium sulfide No.5

Sodium bisulfide NaHS Sodium polysulfide NzqS, x-Z-S) Potassium sulfideK S Potassium bisulfide KHS Calcium sulfide CaS Potassium polysulfide KS, x-Z-S) Sodium diethyl dithiocarbamate (C,H,),NCSSNa Sodiumsulioxylste Na,S0

Sodium sulfite Na,SO,

Sodium hisulfite NIHSO,

Sodium thiosulfate Na,S,0,

Sodium dithionite Ns,S,0,

Sodium pyrosulfite Na,S,O,

Sodium copper sulfite NaCuSO 3 Sodium silver sulfite NaAgSO,

Potassium sulfoxylate K,SO

Potassium sulfite K,SO,

Potassium thiosulfate K,S,O,

Potassium dithionite K,S,O,

Ethylenediamine sodium sulfite NaSSCHNH(Cl-l,)

,NHCSSNa ln accordance with the present invention, any one of theabove-listed compounds is prepared to an aqueous solution (about 1-30percent concentration) which is then applied to exposed, light-sensitivephotographic material. In case of coating, the amount of the aqueoussolution (thls solution will be simply referred to as a fixer"hereafter) will vary depending on the type of a photoactivator used andthe thickness of the light-sensitive layer, but it usually is sufficientin such an amount as used for development of a diazo-type copying paper,i.e. in an amount necessary to moisten the surface of thelight-sensitive photographic material. Thus, a fixing method accordingto the invention can be deemed as semidry process. The fixer may beadded with a binder such as cellulose derivative, vinyl polymer,synthetic rubber, etc.

In case of dipping, the required operation is quite similar to, thefixation of a silver halide photographic material. Depending on theconcentration of the fixer and the film thickness of the light-sensitivelayer, the required dipping time will vary, but it usually is within therange of from several seconds to several minutes. When using a coatingtechnique in fixing, it will be better to use a fixer having a higherconcentration in comparison with the case when dipping is employed. Ineither cases, however, drying of the photographic material by heating ata temperatureof l00l80 C. (by means of hot rolls, hot plates, etc.,having a surface temperature of l00-l C.) after fixation treatment isdesirable to have increased fixing effect, while it makes possible touse a fixer having a lower concentration.

Addition of 2-15 percent of a bufier agent (e.g. sodium carbonate,borax, sodium acetate, sodium dihydrogen phosphate or the like alkalinesubstance) into a fixer serves to increase service life of the fixer byseveral times compared with the nonbuifered fixer. Further in thepresent invention, addition of 2-l0 g. of hydroquinone, metol or similarreducing substance per cc. of a fixer is recommendable to preventdiscoloration of the background and degradation of the resulting image.

As mentioned above, a fixer usable in this invention may contain one ormore additives or adjuvants which are commonly known in the photographicart. Furthermore, a lightsensitive photographic material which comprisesa photoactivator being capable of generating a free radical by theaction of light and a color modifier showing a visible color changethrough the action of said free radical also may contain one or moreauxiliary components.

Illustrative of photoactivators referred to are the following:

[1] Compounds represented by the general formula RCX wherein R is aryl,alkyl, aralkyl, aroyl, alkenyl, hydrogen or halogen, and X is halogen.For example, they include carbon tetrachloride, carbon tetrabromide,hexachloroethane, pentabromoethane, p-nitrobenzotribromide,bromotrichloroethane, hexabromoethane,

benzotrichloride, benzotribromide, jodforrn,tetrachlorotetrahydro-naphthalene, chloral, bromal, l,l,l-tribromo-2-methyl-2-propanal, l, l ,2,2,-tetrabromoethane, 2,2,2-tribromoethanol, trichloroacetamide, dimethyl-Z-propanol, a,a,aa,trichlorotoluene. [II] Compounds represented by the general formulawherein Rx means hydrogen or 1 to 5, same or different substituentsselected from the group consisting of nitro, halogen,

' alkyl, haloalkyl, acetyl, haloacetyl, alkaryl and alkoxy. Theyinclude, for example, o-nitro- 01,11,a-tribromo-acetophenone,m-nitro-a,a,a-tribromoacetophenone, p-nitro-a,a,atribromo-acetophenone,a,a,a-tribromo-acetophenone, a,a,a mtetrabromo-acetophenone,a,a,a-tribromo-3,4- dichloroacetophenone.a,a,a-tribromo-2,S-dimethylacetophenone.a,a,a-p-tetrabromo-acetophenone, a,a,a,a',a ',a'[lll] Compoundsrepresented by the general formula R-SO,

wherein A is a heterocyclic group which may be substituted.

and R R and R individually means H. C] or Br, excepting the case whereall of R,, R and R are hydrogen. They include, for example,m,cu,w-tribromoquinaldine, (0,0)- dibromoquinaldine,2-w,w,m-tribromomethyl-4-methylquinoline, w,w-diChlromethyl-quinoline,wbromolepidine, 2w-bromomethyl-isoquinoline,4-w,w,mtribromomethyl-pyrimidine, 4-phenyl-6-m,w,wtribromopyrimidine,2-w,m,w-trichloromethyl-6-nitrobenzthiazole,lphenyl-3-m,w,w-trichloromethyl-5- pyrazolone, w,w,w-tribr0molepidine,bromomethylate, aw,w-dibromomethyl-4-chl0ropyridine, l-methyl-2(chloromethyl)-benzimideazole, 2,5-ditribromomethyl-3,4-dibromothiophene.

[VI] Compounds represented by the general formula 1, l ltrichlorowherein R is unsubstituted or substituted aryl or heterocyclicgroup, and X X and X individually are H, C1 or Br excepting the casewhere all of X X and X; are hydrogen. Typical examples arehexabromo-dimethyl sulfoxide, pentabromodimethyl sulfoxide,hexabromo-dimethyl sulfone, trichloromethyl-phenyl sulfone,tribromomethyl-phenyl sulfone, trichloromethyl-p-chlorophenyl sulfone,tribomomethylp-nitrophenyl sulfone, sulfone,Z-trichloromethylbenzothiazolyl sulfone-(2), 4,6-dimethyl-pyrimidyl-2-tribromomethyl sulfone, tetrabromo dimethyl sulfone, 2,4-dichlorophenyl-trichloromethyl sulfone, 2-methyl-4-chlorophenyl-trichloromethyl sulfone, 2,5-dimethyl-4-chlorophenyl-trichloromethyl sulfone, 2,4-dichlorophenyltribromomethylsulfone.

As color modifiers, there are known two types. A color 0 modifier of theone type is that which originally is a colorless substance capable ofconverting into colored state by the action of a free radical generatedfrom a photoactivator. Such color modifier is useful in so-callednegative-positive system. A color'modifier of the other type is thatwhich originally has a color, but can be converted into bleached ordifferently colored state by the action of a free radical. Such colormodifier is useful in so-called positive-positive system. Illustrationof these color modifiers are the following; diphenylamine,dibenzylamine, triphenylamine, N-hydroxyethyl-N-ethyl aniline,p,p'-methylenebis (N,N-diethylaniline) and the like amine compounds;leuco bases of such dyes as leuco crystal violet, leuco malachite green,michleris hydrol, leuco methylene blue, etc.; and various classes ofdyes, e.g. diphenylmethane dyes, triphenylmethane dyes, thiazine dyes,oxazine dyes, xanthene dyes, anthraquinone dyes, iminonaphthoquinonedyes, azomethine dyes.

conventionally know sensitizers and color tone-improving agents areusable as auxiliary components. Incorporation of these additives into alight-sensitive photographic material does not injure the effectivenessof fixation according to the present invention.

In summary, a method of the present invention comprises dipping orcoating exposed light-sensitive photographic material into or with anaqueous solution of the beforedefined fixing agent and then, if desired,drying said photographic material by heating. According, it is entirelyfree from generation of noxious vapor or from decrease in imageresolution. This enables us to obtain an excellent and stable copythrough simple operations.

PREFERRED EMBODIMENTS A more detailed explanation of the presentinvention may be had with reference to the following examples EXAMPLE 1A baryta paper (for photographic use) is coated under red safety lightwith a light-sensitive solution of:

Hexabromodimethyl sulfone-S g.

Diphenyl amine-5 g.

Acetone- 100 cc. and then dried. The thus obtained light-sensitivephotographic material is superposed with a photographic negative bearingan original image and the resulted assembly is exposed to light from an800 watt mercury lamp at a distance of 5 cm. for 5 seconds. A dark bluenegative image is obtained on white background.

Then, the photographic material having the negative image is dipped intoa fixer of:

Sodium hydrogen sulfite- 10 g.

Water-100 cc. for 1 minute, to obtain a reproduction which is entirelystable to light exposure.

In another run, the fixer used further contains 5 g. of hydroquinone. Inthis case, the resulting fixed reproduction showed a clean, whitebackground even when stored over a long period.

In the same manner as in example 1, a light-sensitive solution of:

w,m,m-tribromoquinaldine-S g.

N-hydroxyethyl-N-ethylaniline g.

Acetone-100 cc. is coated on a photographic paper which is then dried.The light-sensitive photographic material thus obtained is subjected tolight exposure in the same manner as in example 1 and then passedthrough a wet-diazotype-developing machine in which a fixer of:

Sodium sulfitel 5 g.

Saponine0.3 g.

Water-100 cc. is applied in an amount just sufficient to moisten thesurface of said photographic material. A blue image which is stableagainst further light exposure is obtained.

When the moistened photographic material, after applica tion of thefixer, is dried by heating at 50 C. for 7 seconds, the similar blueimage is obtained. in this case, there may be substituted for the abovefixer:

Sodium sulfite-7 g.

Saponine0.3

Water- 100 cc.

EXAMPLE 3 As in example I, a light-sensitive solution of the followingformulation is coated on baryta paper:

Carbon tetrachloride-5 g.

Diphenylamine-5 g.

Cellulose acetate-l g.

Acet0ne 100 cc. The resulting lighbsensitive photographic material issubjected to light exposure in the same manner as in example 1.whereupon a blue image is obtained. Then, the image-bearing photographicmaterial is dipped for 1 minute in a fixer of the following formulation:

Sodium bisulfide-S g.

Waterl 00 cc. The image becomes stable against further light exposure.

Addition of 7 g. of sodium carbonate to the above fixer serves toincrease the service life of said fixer as much as five times.

EXAMPLE 4 On a white base paper, the surface of which is pretreated witha 10 percent aqueous solution of polyvinyl chloride (polymerizationdegree 600), a light-sensitive solution of the following formulation iscoated:

Tribromomethyl phenyl sulfone-S g.

Ethylaminophenyliminonaphthoquinone-Z.5 g.

Cellulose acetatel g.

Acetone-100 cc.

The light-sensitive photographic material is a bluish green color anduseful in positive-positive system, i.e., bleach-out. Exposure of thephotographic material to light yields a clear bluish green image, whichcan be stabilized in the same manner as in example 2 by using a fixer ofthe following formulation:

Sodium bisulfide-S g.

Water- I 00 cc. The resulted image does not show any color change byfurther light exposure.

EXAMPLE 5 g. Diphenyl aminel 0 g. Acridine Orange-0.l g.

Acetone-1 00 cc. The light-sensitive photographic material obtained issensitive over the wide range of wavelength including a visible region,since it includes a photo-sensitizing dye. The photographic material issubjected to light exposure by imagewise irradiation at a distance of 30cm. and for 15- 1) seconds by means of a slide projector, with a 500 w.tungsten lamp as light source, having an image-bearing photographicnegative placed therein. A clear blue image is obtained. The imagedphotographic material is then treated by using the same apparatus andfixer as used in example 2, to obtain stabilized image which is entirelysafe against further light exposure.

The above examples have been presented for the purpose of illustrationand should not be taken to limit the scope of the present invention. Itwill be apparent that the described exam ples are capable of manyvariations and modifications which are likewise to be included withinthe scope of the present invention as set forth in the appended claims.

What is claimed is:

1. In the method of forming an image which comprises providing animaging material comprising a photoactivator capable of generating ahalogen free radical by the action of light and a color modifier capableof producing a visible color change by the action of said halogen freeradical; exposing said material imagewise to light thereby effectingimagewise halogen free radical generation and a coincident visible colorchange; and fixing the resulting image; the improvement which comprisesa fixing method wherein said material, after light exposure, iscontacted with an aqueous solution of a sulfur compound selected fromthe group consisting of watersoluble salts of hydrogen sulfide andwater-soluble salts of sulfur-containing oxygen acids for a timesufficient to inactivate said photoactivator.

2. The improvement according to Claim 1 comprising the further step ofdrying the material thus contacted at a temperature between about l 80C.

3. The improvement according to Claim 1 wherein said material is coatedwith said solution.

4. The improvement according to Claim 1 wherein said material is dippedinto said solution.

5. The improvement according to claim I wherein said solution furthercomprises up to about 10 percent of a hydroxy benzene reducing agent.

6. The improvement according to claim 2 wherein said drying stepcomprises contacting said material with a surface heated to about C.

2. The improvement according to Claim 1 comprising the further step ofdrying the material thus contacted at a temperature between about100*-180* C.
 3. The improvement according to Claim 1 wherein saidmaterial is coated with said solution.
 4. The improvement according toClaim 1 wherein said material is dipped into said solution.
 5. Theimprovement according to claim 1 wherein said solution further comprisesup to about 10 percent of a hydroxy benzene reducing agent.
 6. Theimprovement according to claim 2 wherein said drying step comprisescontacting said material with a surface heated to about 150* C.